1. Field of the Invention
This invention relates to an ultrasonic transducer and to a method of manufacturing the same.
2. Description of the Prior Art
Ultrasonic transducers are widely employed as the probes in ultrasonic diagnostic equipment for real-time tomography, in ultrasonic materials testing equipment for the non-destructive testing of materials, and in many other applications.
An ultrasonic transducer generally is of a structure that includes a vibrator comprising a piezoelectric element for generating ultrasonic waves conforming to a driving voltage or for converting a received ultrasonic wave into an electric signal, an acoustic matching layer for acoustic impedence matching with a specimen under examination, and a backing member for absorbing both free oscillation of the vibrator and ultrasonic waves that emerge from the back surface, the vibrator, acoustic matching layer and backing being disposed in laminated relation.
Various materials capable of being used as the vibrator of such ultrasonic transducers have been the object of research. One material recently proposed for such use is a film-like piezoelectric polymer member formed from a piezoelectric polymer such as a polyvinylidene fluoride (PVDF) resin. A piezoelectric polymer member such as of PVDF exhibits excellent acoustic matching with respect to a living body since its acoustic impedence is closer to that of a living body than is the acoustic impedence of conventional ceramic piezoelectric members. Such a piezoelectric member also has a low mechanical Q, as a result of which improved sensitivity and response are anticipated, and exhibits flexibility that enables the vibrator to be machined into almost any shape with comparative ease.
To form a vibrator, the piezoelectric member generally is embraced by a pair of electrodes necessary for applying a driving voltage to the piezoelectric member or for detecting a received signal in the form of a voltage, and each electrode must be provided with a lead wire for connecting the electrode to a separately provided transmitter circuit, which supplies the abovementioned driving voltage, or to a separate receiver circuit that receives a signal from the piezoelectric member.
While the above-described prior art has the advantages set forth, problems in manufacture are encountered owing to the fact that a piezoelectric polymer member has little resistance to heat. Specifically, the low heat resistance makes the piezoelectric member susceptible to damage by heat when the lead wires are connected to the electrodes as by soldering. This problem has been an impediment to realizing practical use of a piezoelectric polymer member.